This invention relates to an improved transmission belt and apparatus for its manufacture, particularly double V-type belts.
It is well known that transmission belts are used for transferring power from a driving pulley to a driven pulley by passing the belt in a continuous manner around the pulleys. Often times because of limitations of space or design, it is necessary to utilize a double V-type belt which will transmit power with equal facility and efficiency regardless of the direction of flexure about a neutral axis plane extending longitudinally of the belt.
The double V-type belts have a central strength section and sections on either side which may be considered as either tension or compression sections, depending on the relationship of the belt to the pulley. These belts can be manufactured by concentrically assembling the various sections, cutting them into belt bodies, and vulcanizing them to form an integral structure. A cover fabric may be applied to the belt body prior to vulcanization.
In building up the belt body prior to molding and curing, relatively close tolerances are required to produce a satisfactory belt. The belt body may have a cross-sectional area greater than the cross-sectional area of the mold, in which cause a portion of the stock of the body is squeezed out of the mold. Or, the belt body may have a smaller cross-sectional area than the area of the mold, in which case the strength cord line may be displaced or skewed.
U.S. Pat. No. 3,164,026, issued Jan. 5, 1965 to Terhune, describes a method for manufacturing double V-type belts which comprises adding a blowing agent to the belt body at both sides of the neutral axis, or cord line, and heat curing the belt to blow a limited portion of the body at both sides of the neutral axis to expand and stretch the cover. This method requires an additional manufacturing step in order to incorporate the blowing agent into at least a portion of the stock which makes up the belt body.
U.S. Pat. Nos. 2,518,137, issued Aug. 8, 1950 and 2,602,188, issued July 8, 1952, both to Gorecki, disclose molds for manufacturing single V-type belts, which have resilient means for applying pressure to the inner radial force of the belt during curing. The devices and methods described therein have not been employed in the manufacture of double V-type belts.
Accordingly, it is an object of the present invention to provide an improved apparatus for manufacturing double V-type belts.
Other objects, aspects and advantages of the present invention will be apparent from the accompanying drawings and the following detailed description.